The present invention relates to an article comprising a multilayer film suitable for packaging end use, especially a multilayer film suitable for use in the packaging of moisture and oxygen sensitive products, particularly moisture and oxygen sensitive granular and/or powdered bulk products, such as plastic resin pellets, chemical additives, coffee, or dry pet food. The multilayer film is a laminate of three components wherein the first component comprises an oriented film, and the second component, which is between the first component and the third component, comprises a metallized film. The exposed first component surface is heat-sealable to both itself (end sealable) and the third component surface (lap sealable) while the exposed third component surface is heat-sealable to itself (gusset seal) as well as to the first component (lap sealable). The article preferably comprises a heat seal of the film to itself or another film. The external surface of the article comprises a film layer having a high coefficient of friction in order to improve stackability of the articles. The present invention also relates to packaged products in which the package comprises the article of the invention.
A variety of moisture, light and/or oxygen sensitive products are packaged in foil-based bags or pouches. Metal foil provides excellent gas and moisture barrier properties. However, even when laminated to paper or a plastic web, foil is subject to flex cracking and pinholing during normal handling. The poor abuse resistance of a foil-based structure can quickly obviate the initial low permeability. In order to avoid package failure, a variety of oxygen and moisture sensitive resin pellets often are packaged in foil-based bags formed by a tuber process. By such process a paper/foil laminate or a plastic/foil laminate is attached with glue at limited, preselected intervals to an outer, plastic web. Thus, failure of the inner foil-based wall of the bag does not always result in failure of the outer wall. However, these multiwalled structures are necessarily thick, typically at least 12 to 20 mils, and the outer wall xe2x80x9csafety netxe2x80x9d does not possess moisture and gas barrier properties on the order of those of the foil-based wall, such that failure of the foil-based laminate results in reduction of such properties for the overall bag.
Similarly, there are a variety of photographic products, such as undeveloped photographic film and motion picture rolls, which have for some time been vacuum packaged in opaque, high gas-barrier films. One such film has been a multilayer film having the structure:
polyethylene/foil/nylon/polyethylene terephthalate However, it would be desirable to provide an alternative film which exhibits a high gas-barrier but which does not contain foil.
A variety of metallized films are known in the art. Typically such films are formed by depositing a thin layer of a metal, most typically aluminum, onto a thermoplastic substrate by a process such as vacuum deposition, vapor deposition or sputtering. Many metallized films include a sealant layer. Although metallized films provide excellent moisture and oxygen barrier properties and are pliable, such that they are resistant to flex cracking and pinholing, there remains a need in the art for such a film which is capable of forming a variety of types of seals and which has sufficient mechanical strength to accommodate large quantities of dry flow product in a bulky, heavy mass.
Accordingly, in a first aspect the present invention is directed to a multilayer laminate which includes an oriented sealant film having at least one layer and comprising a first outermost layer of the laminate, wherein the first outermost laminate layer is at least one member selected from the group consisting of polyethylene homopolymer, ethylene/alpha-olefin copolymer, ethylene/ester copolymer, ionomer, copolyamide, propylene copolymer and styrene-butadiene copolymer; a core barrier metallized film which includes a polymeric substrate which is a member selected from the group consisting of polyester, polypropylene, high density polyethylene, and nylon, and a continuous layer of a metal disposed on the polymeric substrate; and an outer film having at least one layer and comprising a second outermost layer of the laminate, wherein the second outermost laminate layer is at least one member selected from the group consisting of polyethylene homopolymer, ethylene/alpha-olefin copolymer, ethylene/ester copolymer, ionomer, copolyamide, propylene copolymer and styrene-butadiene copolymer and
wherein the laminate has a moisture vapor transmission rate of less than about 0.1 g/100 sq. in. and an instrumented impact strength of at least 2.0 Joules.
In a preferred embodiment the present invention is directed to a multilayer laminate which includes an oriented sealant film having at least
a first layer of polyethylene homopolymer, ethylene/alpha-olefin copolymer, ethylene/ester copolymer, ionomer, copolyamide, propylene copolymer or styrene-butadiene copolymer;
a second layer of ethylene/ester copolymer, modified polyolefin, ionomer, ethylene acrylate copolymer, or ethylene (meth)acrylic acid;
a third layer of ethylene/ester copolymer, modified polyolefin, ionomer, ethylene acrylate copolymer, or ethylene (meth)acrylic acid; and
a fourth layer of polyethylene homopolymer, ethylene/alpha-olefin copolymer, ethylene/ester copolymer, ionomer, copolyamide, propylene copolymer or styrene-butadiene copolymer;
a core barrier metallized film having
a polymeric substrate of polyester, polypropylene, high density polyethylene, or nylon; and
a continuous layer of a metal disposed on the polymeric substrate; and an outer film having at least one layer and including an outermost layer of the laminate, where the outermost laminate layer is polyethylene homopolymer, ethylene/alpha-olefin copolymer, ethylene/ester copolymer, ionomer, copolyamide, propylene copolymer or styrene-butadiene copolymer.
Preferably, the laminate includes an adhesive disposed between the sealant film and the core barrier film and an adhesive disposed between the outer film and the core barrier film. Optionally, the laminate may include more than one barrier metallized film. Preferably, the laminate has a total thickness of from about 3.0 to about 15.0 mils.
In a preferred embodiment the polymeric substrate of the core barrier metallized film is polyester. In a more preferred embodiment the core barrier metallized film also includes a layer of polyethylene naphthalate. It is preferred that the metal of the metallized film is aluminum.
Optionally, the oriented sealant film may include a pigment.
In a second aspect, the present invention is directed to a moisture and oxygen barrier bag formed of the laminate of the present invention. As the outermost layer of the sealant film is sealable both to itself and to the outermost layer of the outer film and as the outermost layer of the outer film is sealable both to itself and to the outermost layer of the sealant film both lap seals (inside to outside) and fin seals (inside to inside and outside to outside) may be formed. Thus, the bag may include a variety of seal types including gusset seals.
Optionally, the outer film may include reverse printing on the surface adjacent the adhesive, i.e. the surface opposite to the outermost surface.